Tumor tissue contains not only cancer cells but also many immune cells. At an early stage of tumor tissue formation, growth of tumor tissue is suppressed by anticancer activity of immune cells and cancer cells are eliminated from the body. However, when the anticancer activity of the immune cells is weakened, tumor tissue continues to grow and in some cases metastasis of the tumor tissue may occur. A therapy in which the immune cells in tumor tissue are activated to kill cancer cells is called cancer immunotherapy, which has attracted attention in recent years. In conventional cancer immunotherapy, cytotoxic T cells and natural killer cells are activated by overdose of Interleukin-2 (IL-2). However, tumor tissue does not have a mechanism to specifically take up IL-2 and IL-2 is systemically overdosed under the current situation, and thus significant toxicity has been observed. In addition, there is another problem to be solved in that activation of immune cells is limited under the environment of the tumor in which cancer cells have started secretion of a cytokine called tumor growth factor or transforming growth factor (TGF-β).